1. Field of Invention
The present disclosure relates to an electronic circuit substrate and a method of manufacturing the electronic circuit substrate. More particularly, the present disclosure relates to a metal substrate and a method of manufacturing the metal substrate.
2. Description of Related Art
A printed circuit board is an indispensable material in electronic products. A demand of the printed circuit board is increased with a growing demand of consumer electronic products. With the development toward compact size and flexibility for the electronic products, a flexible printed circuit board is widely applied recently in computers and its peripheral equipment, communication products and consumer electronic products because of its features able to be bent and be three-dimensionally wired.
A typical flexible printed circuit board is a composite board constituted by a dielectric substrate, such as resin, glass fiber or other plastic materials, and a conductive layer, such as copper foil or other metal material layers. For example, a flexible copper dad laminate is constituted by a polyimide (PI) substrate as the dielectric substrate, and a non-adhesive single-sided copper foil coated or bonded on the PI substrate using a casting method or a lamination method.
Recently, it is required for the flexible printed circuit board to be ultra-thin, high density of components and multifunction, in that an electronic system is becoming compact and low cost. However, fold damage, pad damage or delamination (or called as blistering) may occur in a single layer PI substrate for manufacturing an ultra-thin flexible printed circuit board during processing due to inadequate stiffness of the substrate, and thus to affect production yield and dimensional stability. For this reason, an adhesive layer formed on a surface of the single layer PI substrate using a coating method or a transfer printing method and a reinforcing layer overlying the adhesive layer are introduced and a lamination is then performed to let the reinforcing layer tightly adhere to the PI substrate to obtain a composite structure and to reinforce the ultra-thin copper clad substrate, and thus to increase yield thereof.
However, during the thermal lamination with high temperature and high pressure, the adhesive may be fused and bonded to the PI substrate. The adhesive may be remained during the reinforcing layer is tore off, which results in increasing of product defect rate. If the reinforcing layer is retained, the thickness of the flexible printed circuit board is increased. Therefore, there is a need for an advanced printed circuit board and a method of manufacturing the same to solve problems in prior art.